As her concert wound down Friday at the Riviera, Leslie Feist stood amid a sea of fans that she had invited on stage to slow dance.

“Hold that person close and listen to a song about how it could all fall apart tomorrow,” she said with a hint of a smile.

“Let it Die” isn’t exactly the typical rousing set-closer one would expect from a performer who’s become a star in recent years, prominent enough to draw a healthy crowd to the Riv, including Mayor Rahm Emanuel and his wife, Amy.

But this was no ordinary concert, as the Toronto singer-songwriter shook up her songbook and brought an earthier, grittier feel to her music, more akin to a field recording with better mood lighting than a pop extravaganza for a diva on the rise.

When last seen four years ago, Feist was doing a little Busby Berkeley-style dancing in a TV commercial that effectively advertised not only a portable MP3 player but her latest single, “1234.”

Both the song and the singer found a big audience – a burst of mainstream glitz for a performer who had been dabbling in arty projects since the ‘90s. Previously, Feist had toured with Toronto indie band Broken Social Scene and disco-provocateur Peaches, then refashioned herself as a folk-pop singer. “Mushaboom” and “1234” brought her a measure of fame, but she returned this year with a somber, low-key album, “Metals,” and a determination to keep things loose rather than follow the industry-prescribed career path.

At Friday’s show, “1234” was nowhere to be heard, and “Mushaboom” was radically altered, its bouncy melody undermined as her drummer thwacked away with what looked like a couple of wood slats. Instead she put the focus squarely on her newer songs, and even they took on altered personalities that trumped the studio versions.

With three musicians and three singers focusing on rhythm as much as melody, the music shivered and shimmied. Feist stomped the stage in time to the beat and the rattle of tambourines for the opening “Undiscovered First,” placing the song in a psychic zone somewhere between an Appalachian campfire and a Southern Baptist church service. “Graveyard” turned into a spooky anthem suitable for the “Walking Dead” TV series with its recurring refrain of “Bring ‘em all back to life.” Voices turned into wordless percussion instruments on the rousing “A Commotion.”

At the center of it all was Feist’s brilliantly understated guitar. She brushed the strings to create shimmering washes of drone or bent them into rusty blue-note shapes. She set the rhythmic pulse, then fractured it, shadow-boxing with the beat like Keith Richards.

There were familiar reference points for Feist fans who prefer her milder coffeehouse guise. The music would give way and her voice settled into a warm alto that was confiding, unhurried, the hushed crowd attentive to every nuance, held rapt by the bossa nova sway of “So Sorry” or the four-part harmonies of “Cicadas and Gulls.”

But there wasn’t anything precious or tentative about this show – which wasn’t the case when she played the same venue in 2007. Back then, Feist seemed almost constrained by her sudden emergence into the mainstream. Now she clearly felt comfortable enough to let a little grime and grease creep into even her most delicate songs.